In known ion engines, the primary plasma from which the ion beam is extracted is obtained in the discharge chamber in two basic ways:
a) by using plasma source based on continuous discharge between an anode and a cathode capable of emitting electrons (a hot filament or a hollow cathode which is heated and may be equipped with an electrode called a "keeper") which, when accelerated in the presence of a static magnetic field, produce the ionization of the gas present in the discharge chamber;
b) by exciting the gas present in the discharge chamber with an electromagnetic field at radio frequency (order of magnitude of the frequency: several MHz).